* @ingroup Cache
* @since 1.26
*/
-class WANObjectCache implements IExpiringStore, LoggerAwareInterface {
+class WANObjectCache implements IExpiringStore, IStoreKeyEncoder, LoggerAwareInterface {
/** @var BagOStuff The local datacenter cache */
protected $cache;
/** @var MapCacheLRU[] Map of group PHP instance caches */
protected $asyncHandler;
/** @var float Unix timestamp of the oldest possible valid values */
protected $epoch;
+ /** @var string Stable secret used for hasing long strings into key components */
+ protected $secret;
/** @var int Callback stack depth for getWithSetCallback() */
private $callbackDepth = 0;
const COOLOFF_TTL = 1;
/** Default remaining TTL at which to consider pre-emptive regeneration */
const LOW_TTL = 30;
+ /** Max TTL to store keys when a data sourced is lagged */
+ const TTL_LAGGED = 30;
/** Never consider performing "popularity" refreshes until a key reaches this age */
const AGE_NEW = 60;
/** Seconds to ramp up to the "popularity" refresh chance after a key is no longer new */
const RAMPUP_TTL = 30;
- /** Idiom for getWithSetCallback() callbacks to avoid calling set() */
+ /** Idiom for getWithSetCallback() meaning "do not store the callback result" */
const TTL_UNCACHEABLE = -1;
- /** Idiom for getWithSetCallback() callbacks to 'lockTSE' logic */
+ /** Idiom for getWithSetCallback() meaning "no regeneration mutex based on key hotness" */
const TSE_NONE = -1;
- /** Max TTL to store keys when a data sourced is lagged */
- const TTL_LAGGED = 30;
- /** Idiom for delete() for "no hold-off" */
- const HOLDOFF_NONE = 0;
- /** Idiom for set()/getWithSetCallback() for "do not augment the storage medium TTL" */
+ /** Idiom for set()/getWithSetCallback() meaning "no post-expiration persistence" */
const STALE_TTL_NONE = 0;
- /** Idiom for set()/getWithSetCallback() for "no post-expired grace period" */
+ /** Idiom for set()/getWithSetCallback() meaning "no post-expiration grace period" */
const GRACE_TTL_NONE = 0;
+ /** Idiom for delete()/touchCheckKey() meaning "no hold-off period for cache writes" */
+ const HOLDOFF_NONE = 0;
- /** Idiom for getWithSetCallback() for "no minimum required as-of timestamp" */
+ /** Idiom for getWithSetCallback() meaning "no minimum required as-of timestamp" */
const MIN_TIMESTAMP_NONE = 0.0;
+ /** @var int One second into the UNIX timestamp epoch */
+ const EPOCH_UNIX_ONE_SECOND = 1.0;
/** Tiny negative float to use when CTL comes up >= 0 due to clock skew */
const TINY_NEGATIVE = -0.000001;
/** Tiny positive float to use when using "minTime" to assert an inequality */
const TINY_POSTIVE = 0.000001;
- /** Milliseconds of delay after get() where set() storms are a consideration with 'lockTSE' */
+ /** Milliseconds of delay after get() where set() storms are a consideration with "lockTSE" */
const SET_DELAY_HIGH_MS = 50;
/** Min millisecond set() backoff for keys in hold-off (far less than INTERIM_KEY_TTL) */
const RECENT_SET_LOW_MS = 50;
/** Max millisecond set() backoff for keys in hold-off (far less than INTERIM_KEY_TTL) */
const RECENT_SET_HIGH_MS = 100;
+ /** @var int Seconds needed for value generation considered slow */
+ const GENERATION_SLOW_SEC = 3;
+
/** Parameter to get()/getMulti() to return extra information by reference */
const PASS_BY_REF = -1;
/** Cache format version number */
const VERSION = 1;
- const FLD_VERSION = 0; // key to cache version number
+ const FLD_FORMAT_VERSION = 0; // key to WAN cache version number
const FLD_VALUE = 1; // key to the cached value
const FLD_TTL = 2; // key to the original TTL
- const FLD_TIME = 3; // key to the cache time
+ const FLD_TIME = 3; // key to the cache timestamp
const FLD_FLAGS = 4; // key to the flags bitfield (reserved number)
- const FLD_HOLDOFF = 5; // key to any hold-off TTL
+ const FLD_VALUE_VERSION = 5; // key to collection cache version number
+ const FLD_GENERATION_TIME = 6; // key to how long it took to generate the value
+
+ const PURGE_TIME = 0; // key to the tombstone entry timestamp
+ const PURGE_HOLDOFF = 1; // key to the tombstone entry hold-off TTL
const VALUE_KEY_PREFIX = 'WANCache:v:';
const INTERIM_KEY_PREFIX = 'WANCache:i:';
const PURGE_VAL_PREFIX = 'PURGED:';
- const VFLD_DATA = 'WOC:d'; // key to the value of versioned data
- const VFLD_VERSION = 'WOC:v'; // key to the version of the value present
-
const PC_PRIMARY = 'primary:1000'; // process cache name and max key count
/**
* is configured to interpret /<region>/<cluster>/ key prefixes as routes. This
* requires that "region" and "cluster" are both set above. [optional]
* - epoch: lowest UNIX timestamp a value/tombstone must have to be valid. [optional]
+ * - secret: stable secret used for hashing long strings into key components. [optional]
*/
public function __construct( array $params ) {
$this->cache = $params['cache'];
$this->region = $params['region'] ?? 'main';
$this->cluster = $params['cluster'] ?? 'wan-main';
$this->mcrouterAware = !empty( $params['mcrouterAware'] );
- $this->epoch = $params['epoch'] ?? 1.0;
+ $this->epoch = $params['epoch'] ?? self::EPOCH_UNIX_ONE_SECOND;
+ $this->secret = $params['secret'] ?? (string)$this->epoch;
$this->setLogger( $params['logger'] ?? new NullLogger() );
$this->stats = $params['stats'] ?? new NullStatsdDataFactory();
* Consider using getWithSetCallback() instead of get() and set() cycles.
* That method has cache slam avoiding features for hot/expensive keys.
*
- * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a cache key info map.
+ * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a cache key metadata map.
* This map includes the following metadata:
* - asOf: UNIX timestamp of the value or null if the key is nonexistant
* - tombAsOf: UNIX timestamp of the tombstone or null if the key is not tombstoned
* - lastCKPurge: UNIX timestamp of the highest check key or null if none provided
+ * - version: cached value version number or null if the key is nonexistant
*
* Otherwise, $info will transform into the cached value timestamp.
*
* @param string $key Cache key made from makeKey() or makeGlobalKey()
* @param mixed|null &$curTTL Approximate TTL left on the key if present/tombstoned [returned]
- * @param array $checkKeys List of "check" keys
+ * @param string[] $checkKeys The "check" keys used to validate the value
* @param mixed|null &$info Key info if WANObjectCache::PASS_BY_REF [returned]
* @return mixed Value of cache key or false on failure
*/
$info = [
'asOf' => $infoByKey[$key]['asOf'] ?? null,
'tombAsOf' => $infoByKey[$key]['tombAsOf'] ?? null,
- 'lastCKPurge' => $infoByKey[$key]['lastCKPurge'] ?? null
+ 'lastCKPurge' => $infoByKey[$key]['lastCKPurge'] ?? null,
+ 'version' => $infoByKey[$key]['version'] ?? null
];
} else {
$info = $infoByKey[$key]['asOf'] ?? null; // b/c
* Fetch the value of several keys from cache
*
* Pass $info as WANObjectCache::PASS_BY_REF to transform it into a map of cache keys
- * to cache key info maps, each having the same style as those of WANObjectCache::get().
+ * to cache key metadata maps, each having the same style as those of WANObjectCache::get().
* All the cache keys listed in $keys will have an entry.
*
* Othwerwise, $info will transform into a map of (cache key => cached value timestamp).
* Only the cache keys listed in $keys that exists or are tombstoned will have an entry.
*
+ * $checkKeys holds the "check" keys used to validate values of applicable keys. The integer
+ * indexes hold "check" keys that apply to all of $keys while the string indexes hold "check"
+ * keys that only apply to the cache key with that name.
+ *
* @see WANObjectCache::get()
*
- * @param array $keys List of cache keys made from makeKey() or makeGlobalKey()
+ * @param string[] $keys List of cache keys made from makeKey() or makeGlobalKey()
* @param mixed|null &$curTTLs Map of (key => TTL left) for existing/tombstoned keys [returned]
- * @param array $checkKeys List of check keys to apply to all $keys. May also apply "check"
- * keys to specific cache keys only by using cache keys as keys in the $checkKeys array.
+ * @param string[]|string[][] $checkKeys Map of (integer or cache key => "check" key(s))
* @param mixed|null &$info Map of (key => info) if WANObjectCache::PASS_BY_REF [returned]
- * @return array Map of (key => value) for keys that exist and are not tombstoned
+ * @return mixed[] Map of (key => value) for existing values; order of $keys is preserved
*/
final public function getMulti(
array $keys,
// Get the main cache value for each key and validate them
foreach ( $valueKeys as $vKey ) {
$key = substr( $vKey, $vPrefixLen ); // unprefix
- list( $value, $curTTL, $asOf, $tombAsOf ) = isset( $wrappedValues[$vKey] )
- ? $this->unwrap( $wrappedValues[$vKey], $now )
- : [ false, null, null, null ]; // not found
+ list( $value, $keyInfo ) = $this->unwrap( $wrappedValues[$vKey] ?? false, $now );
// Force dependent keys to be seen as stale for a while after purging
// to reduce race conditions involving stale data getting cached
$purgeValues = $purgeValuesForAll;
$lastCKPurge = null; // timestamp of the highest check key
foreach ( $purgeValues as $purge ) {
- $lastCKPurge = max( $purge[self::FLD_TIME], $lastCKPurge );
- $safeTimestamp = $purge[self::FLD_TIME] + $purge[self::FLD_HOLDOFF];
- if ( $value !== false && $safeTimestamp >= $asOf ) {
+ $lastCKPurge = max( $purge[self::PURGE_TIME], $lastCKPurge );
+ $safeTimestamp = $purge[self::PURGE_TIME] + $purge[self::PURGE_HOLDOFF];
+ if ( $value !== false && $safeTimestamp >= $keyInfo['asOf'] ) {
// How long ago this value was invalidated by *this* check key
- $ago = min( $purge[self::FLD_TIME] - $now, self::TINY_NEGATIVE );
+ $ago = min( $purge[self::PURGE_TIME] - $now, self::TINY_NEGATIVE );
// How long ago this value was invalidated by *any* known check key
- $curTTL = min( $curTTL, $ago );
+ $keyInfo['curTTL'] = min( $keyInfo['curTTL'], $ago );
}
}
+ $keyInfo[ 'lastCKPurge'] = $lastCKPurge;
if ( $value !== false ) {
$result[$key] = $value;
}
- if ( $curTTL !== null ) {
- $curTTLs[$key] = $curTTL;
+ if ( $keyInfo['curTTL'] !== null ) {
+ $curTTLs[$key] = $keyInfo['curTTL'];
}
$infoByKey[$key] = ( $info === self::PASS_BY_REF )
- ? [ 'asOf' => $asOf, 'tombAsOf' => $tombAsOf, 'lastCKPurge' => $lastCKPurge ]
- : $asOf; // b/c
+ ? $keyInfo
+ : $keyInfo['asOf']; // b/c
}
$info = $infoByKey;
/**
* @since 1.27
- * @param array $timeKeys List of prefixed time check keys
- * @param array $wrappedValues
+ * @param string[] $timeKeys List of prefixed time check keys
+ * @param mixed[] $wrappedValues
* @param float $now
- * @return array List of purge value arrays
+ * @return array[] List of purge value arrays
*/
private function processCheckKeys( array $timeKeys, array $wrappedValues, $now ) {
$purgeValues = [];
* @param mixed $value
* @param int $ttl Seconds to live. Special values are:
* - WANObjectCache::TTL_INDEFINITE: Cache forever (default)
+ * - WANObjectCache::TTL_UNCACHEABLE: Do not cache (if the key exists, it is not deleted)
* @param array $opts Options map:
- * - lag: seconds of replica DB lag. Typically, this is either the replica DB lag
+ * - lag: Seconds of replica DB lag. Typically, this is either the replica DB lag
* before the data was read or, if applicable, the replica DB lag before
* the snapshot-isolated transaction the data was read from started.
* Use false to indicate that replication is not running.
* the current time the data was read or (if applicable) the time when
* the snapshot-isolated transaction the data was read from started.
* Default: 0 seconds
- * - pending: whether this data is possibly from an uncommitted write transaction.
+ * - pending: Whether this data is possibly from an uncommitted write transaction.
* Generally, other threads should not see values from the future and
* they certainly should not see ones that ended up getting rolled back.
* Default: false
- * - lockTSE: if excessive replication/snapshot lag is detected, then store the value
+ * - lockTSE: If excessive replication/snapshot lag is detected, then store the value
* with this TTL and flag it as stale. This is only useful if the reads for this key
* use getWithSetCallback() with "lockTSE" set. Note that if "staleTTL" is set
* then it will still add on to this TTL in the excessive lag scenario.
* Default: WANObjectCache::TSE_NONE
- * - staleTTL: seconds to keep the key around if it is stale. The get()/getMulti()
+ * - staleTTL: Seconds to keep the key around if it is stale. The get()/getMulti()
* methods return such stale values with a $curTTL of 0, and getWithSetCallback()
* will call the regeneration callback in such cases, passing in the old value
* and its as-of time to the callback. This is useful if adaptiveTTL() is used
* on the old value's as-of time when it is verified as still being correct.
- * Default: WANObjectCache::STALE_TTL_NONE.
- * - creating: optimize for the case where the key does not already exist.
+ * Default: WANObjectCache::STALE_TTL_NONE
+ * - creating: Optimize for the case where the key does not already exist.
* Default: false
+ * - version: Integer version number signifiying the format of the value.
+ * Default: null
+ * - walltime: How long the value took to generate in seconds. Default: 0.0
* @note Options added in 1.28: staleTTL
* @note Options added in 1.33: creating
+ * @note Options added in 1.34: version, walltime
* @return bool Success
*/
final public function set( $key, $value, $ttl = self::TTL_INDEFINITE, array $opts = [] ) {
$now = $this->getCurrentTime();
+ $lag = $opts['lag'] ?? 0;
+ $age = isset( $opts['since'] ) ? max( 0, $now - $opts['since'] ) : 0;
+ $pending = $opts['pending'] ?? false;
$lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
$staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
- $age = isset( $opts['since'] ) ? max( 0, $now - $opts['since'] ) : 0;
$creating = $opts['creating'] ?? false;
- $lag = $opts['lag'] ?? 0;
+ $version = $opts['version'] ?? null;
+ $walltime = $opts['walltime'] ?? 0.0;
+
+ if ( $ttl < 0 ) {
+ return true;
+ }
// Do not cache potentially uncommitted data as it might get rolled back
- if ( !empty( $opts['pending'] ) ) {
+ if ( $pending ) {
$this->logger->info(
'Rejected set() for {cachekey} due to pending writes.',
[ 'cachekey' => $key ]
}
// Wrap that value with time/TTL/version metadata
- $wrapped = $this->wrap( $value, $logicalTTL ?: $ttl, $now );
+ $wrapped = $this->wrap( $value, $logicalTTL ?: $ttl, $version, $now, $walltime );
$storeTTL = $ttl + $staleTTL;
if ( $creating ) {
* @see WANObjectCache::getCheckKeyTime()
* @see WANObjectCache::getWithSetCallback()
*
- * @param array $keys
+ * @param string[] $keys
* @return float[] Map of (key => UNIX timestamp)
* @since 1.31
*/
foreach ( $rawKeys as $key => $rawKey ) {
$purge = $this->parsePurgeValue( $rawValues[$rawKey] );
if ( $purge !== false ) {
- $time = $purge[self::FLD_TIME];
+ $time = $purge[self::PURGE_TIME];
} else {
// Casting assures identical floats for the next getCheckKeyTime() calls
$now = (string)$this->getCurrentTime();
* @note Callable type hints are not used to avoid class-autoloading
*/
final public function getWithSetCallback( $key, $ttl, $callback, array $opts = [] ) {
+ $version = $opts['version'] ?? null;
$pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
-
- // Try the process cache if enabled and the cache callback is not within a cache callback.
- // Process cache use in nested callbacks is not lag-safe with regard to HOLDOFF_TTL since
- // the in-memory value is further lagged than the shared one since it uses a blind TTL.
- if ( $pcTTL >= 0 && $this->callbackDepth == 0 ) {
- $group = $opts['pcGroup'] ?? self::PC_PRIMARY;
- $procCache = $this->getProcessCache( $group );
- $value = $procCache->has( $key, $pcTTL ) ? $procCache->get( $key ) : false;
- } else {
- $procCache = false;
- $value = false;
+ $pCache = ( $pcTTL >= 0 )
+ ? $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY )
+ : null;
+
+ // Use the process cache if requested as long as no outer cache callback is running.
+ // Nested callback process cache use is not lag-safe with regard to HOLDOFF_TTL since
+ // process cached values are more lagged than persistent ones as they are not purged.
+ if ( $pCache && $this->callbackDepth == 0 ) {
+ $cached = $pCache->get( $this->getProcessCacheKey( $key, $version ), INF, false );
+ if ( $cached !== false ) {
+ return $cached;
+ }
}
- if ( $value === false ) {
- // Fetch the value over the network
- if ( isset( $opts['version'] ) ) {
- $version = $opts['version'];
- $asOf = null;
- $cur = $this->doGetWithSetCallback(
- $key,
- $ttl,
- function ( $oldValue, &$ttl, &$setOpts, $oldAsOf )
- use ( $callback, $version ) {
- if ( is_array( $oldValue )
- && array_key_exists( self::VFLD_DATA, $oldValue )
- && array_key_exists( self::VFLD_VERSION, $oldValue )
- && $oldValue[self::VFLD_VERSION] === $version
- ) {
- $oldData = $oldValue[self::VFLD_DATA];
- } else {
- // VFLD_DATA is not set if an old, unversioned, key is present
- $oldData = false;
- $oldAsOf = null;
- }
-
- return [
- self::VFLD_DATA => $callback( $oldData, $ttl, $setOpts, $oldAsOf ),
- self::VFLD_VERSION => $version
- ];
- },
- $opts,
- $asOf
- );
- if ( $cur[self::VFLD_VERSION] === $version ) {
- // Value created or existed before with version; use it
- $value = $cur[self::VFLD_DATA];
- } else {
- // Value existed before with a different version; use variant key.
- // Reflect purges to $key by requiring that this key value be newer.
- $value = $this->doGetWithSetCallback(
- $this->makeGlobalKey( 'WANCache-key-variant', md5( $key ), $version ),
- $ttl,
- $callback,
- // Regenerate value if not newer than $key
- [ 'version' => null, 'minAsOf' => $asOf ] + $opts
- );
- }
- } else {
- $value = $this->doGetWithSetCallback( $key, $ttl, $callback, $opts );
- }
+ $res = $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
+ list( $value, $valueVersion, $curAsOf ) = $res;
+ if ( $valueVersion !== $version ) {
+ // Current value has a different version; use the variant key for this version.
+ // Regenerate the variant value if it is not newer than the main value at $key
+ // so that purges to the main key propagate to the variant value.
+ list( $value ) = $this->fetchOrRegenerate(
+ $this->makeGlobalKey( 'WANCache-key-variant', md5( $key ), $version ),
+ $ttl,
+ $callback,
+ [ 'version' => null, 'minAsOf' => $curAsOf ] + $opts
+ );
+ }
- // Update the process cache if enabled
- if ( $procCache && $value !== false ) {
- $procCache->set( $key, $value );
- }
+ // Update the process cache if enabled
+ if ( $pCache && $value !== false ) {
+ $pCache->set( $this->getProcessCacheKey( $key, $version ), $value );
}
return $value;
* @param int $ttl
* @param callable $callback
* @param array $opts Options map for getWithSetCallback()
- * @param float|null &$asOf Cache generation timestamp of returned value [returned]
- * @return mixed
+ * @return array Ordered list of the following:
+ * - Cached or regenerated value
+ * - Cached or regenerated value version number or null if not versioned
+ * - Timestamp of the cached value or null if there is no value
* @note Callable type hints are not used to avoid class-autoloading
*/
- protected function doGetWithSetCallback( $key, $ttl, $callback, array $opts, &$asOf = null ) {
- $lowTTL = $opts['lowTTL'] ?? min( self::LOW_TTL, $ttl );
- $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
- $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
- $graceTTL = $opts['graceTTL'] ?? self::GRACE_TTL_NONE;
+ private function fetchOrRegenerate( $key, $ttl, $callback, array $opts ) {
$checkKeys = $opts['checkKeys'] ?? [];
- $busyValue = $opts['busyValue'] ?? null;
- $popWindow = $opts['hotTTR'] ?? self::HOT_TTR;
+ $graceTTL = $opts['graceTTL'] ?? self::GRACE_TTL_NONE;
+ $minAsOf = $opts['minAsOf'] ?? self::MIN_TIMESTAMP_NONE;
+ $hotTTR = $opts['hotTTR'] ?? self::HOT_TTR;
+ $lowTTL = $opts['lowTTL'] ?? min( self::LOW_TTL, $ttl );
$ageNew = $opts['ageNew'] ?? self::AGE_NEW;
- $minTime = $opts['minAsOf'] ?? self::MIN_TIMESTAMP_NONE;
- $needsVersion = isset( $opts['version'] );
$touchedCb = $opts['touchedCallback'] ?? null;
$initialTime = $this->getCurrentTime();
$kClass = $this->determineKeyClassForStats( $key );
- // Get the current key value
+ // Get the current key value and its metadata
$curTTL = self::PASS_BY_REF;
$curInfo = self::PASS_BY_REF; /** @var array $curInfo */
$curValue = $this->get( $key, $curTTL, $checkKeys, $curInfo );
// Apply any $touchedCb invalidation timestamp to get the "last purge timestamp"
list( $curTTL, $LPT ) = $this->resolveCTL( $curValue, $curTTL, $curInfo, $touchedCb );
- // Keep track of the best candidate value and its timestamp
- $value = $curValue; // return value
- $asOf = $curInfo['asOf']; // return value timestamp
-
- // Determine if a cached value regeneration is needed or desired
+ // Use the cached value if it exists and is not due for synchronous regeneration
if (
- $this->isValid( $value, $needsVersion, $asOf, $minTime ) &&
+ $this->isValid( $curValue, $curInfo['asOf'], $minAsOf ) &&
$this->isAliveOrInGracePeriod( $curTTL, $graceTTL )
) {
$preemptiveRefresh = (
$this->worthRefreshExpiring( $curTTL, $lowTTL ) ||
- $this->worthRefreshPopular( $asOf, $ageNew, $popWindow, $initialTime )
+ $this->worthRefreshPopular( $curInfo['asOf'], $ageNew, $hotTTR, $initialTime )
);
-
if ( !$preemptiveRefresh ) {
$this->stats->increment( "wanobjectcache.$kClass.hit.good" );
- return $value;
+ return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
} elseif ( $this->scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) ) {
$this->stats->increment( "wanobjectcache.$kClass.hit.refresh" );
- return $value;
+ return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
}
}
+ // Determine if there is stale or volatile cached value that is still usable
$isKeyTombstoned = ( $curInfo['tombAsOf'] !== null );
if ( $isKeyTombstoned ) {
- // Get the interim key value since the key is tombstoned (write-holed)
- list( $value, $asOf ) = $this->getInterimValue( $key, $needsVersion, $minTime );
+ // Key is write-holed; use the (volatile) interim key as an alternative
+ list( $possValue, $possInfo ) = $this->getInterimValue( $key, $minAsOf );
// Update the "last purge time" since the $touchedCb timestamp depends on $value
- $LPT = $this->resolveTouched( $value, $LPT, $touchedCb );
+ $LPT = $this->resolveTouched( $possValue, $LPT, $touchedCb );
+ } else {
+ $possValue = $curValue;
+ $possInfo = $curInfo;
}
- // Reduce mutex and cache set spam while keys are in the tombstone/holdoff period by
- // checking if $value was genereated by a recent thread much less than a second ago.
+ // Avoid overhead from callback runs, regeneration locks, and cache sets during
+ // hold-off periods for the key by reusing very recently generated cached values
if (
- $this->isValid( $value, $needsVersion, $asOf, $minTime, $LPT ) &&
- $this->isVolatileValueAgeNegligible( $initialTime - $asOf )
+ $this->isValid( $possValue, $possInfo['asOf'], $minAsOf, $LPT ) &&
+ $this->isVolatileValueAgeNegligible( $initialTime - $possInfo['asOf'] )
) {
$this->stats->increment( "wanobjectcache.$kClass.hit.volatile" );
- return $value;
+ return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
}
- // Decide if only one thread should handle regeneration at a time
- $useMutex =
+ $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
+ $busyValue = $opts['busyValue'] ?? null;
+ $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
+ $version = $opts['version'] ?? null;
+
+ // Determine whether one thread per datacenter should handle regeneration at a time
+ $useRegenerationLock =
// Note that since tombstones no-op set(), $lockTSE and $curTTL cannot be used to
// deduce the key hotness because |$curTTL| will always keep increasing until the
// tombstone expires or is overwritten by a new tombstone. Also, even if $lockTSE
( $curTTL !== null && $curTTL <= 0 && abs( $curTTL ) <= $lockTSE ) ||
// Assume a key is hot if there is no value and a busy fallback is given.
// This avoids stampedes on eviction or preemptive regeneration taking too long.
- ( $busyValue !== null && $value === false );
-
- $hasLock = false;
- if ( $useMutex ) {
- // Acquire a datacenter-local non-blocking lock
- if ( $this->cache->add( self::MUTEX_KEY_PREFIX . $key, 1, self::LOCK_TTL ) ) {
- // Lock acquired; this thread will recompute the value and update cache
- $hasLock = true;
- } elseif ( $this->isValid( $value, $needsVersion, $asOf, $minTime ) ) {
- // Lock not acquired and a stale value exists; use the stale value
- $this->stats->increment( "wanobjectcache.$kClass.hit.stale" );
-
- return $value;
- } else {
- // Lock not acquired and no stale value exists
- if ( $busyValue !== null ) {
- // Use the busy fallback value if nothing else
- $miss = is_infinite( $minTime ) ? 'renew' : 'miss';
+ ( $busyValue !== null && $possValue === false );
+
+ // If a regeneration lock is required, threads that do not get the lock will use any
+ // available stale or volatile value. If there is none, then the cheap/placeholder
+ // value from $busyValue will be used if provided; failing that, all threads will try
+ // to regenerate the value and ignore the lock.
+ if ( $useRegenerationLock ) {
+ $hasLock = $this->cache->add( self::MUTEX_KEY_PREFIX . $key, 1, self::LOCK_TTL );
+ if ( !$hasLock ) {
+ if ( $this->isValid( $possValue, $possInfo['asOf'], $minAsOf ) ) {
+ $this->stats->increment( "wanobjectcache.$kClass.hit.stale" );
+
+ return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
+ } elseif ( $busyValue !== null ) {
+ $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
$this->stats->increment( "wanobjectcache.$kClass.$miss.busy" );
- return is_callable( $busyValue ) ? $busyValue() : $busyValue;
+ return [
+ is_callable( $busyValue ) ? $busyValue() : $busyValue,
+ $version,
+ $curInfo['asOf']
+ ];
}
}
+ } else {
+ $hasLock = false;
}
- if ( !is_callable( $callback ) ) {
- throw new InvalidArgumentException( "Invalid cache miss callback provided." );
- }
-
- $preCallbackTime = $this->getCurrentTime();
- // Generate the new value from the callback...
+ // Generate the new value given any prior value with a matching version
$setOpts = [];
+ $preCallbackTime = $this->getCurrentTime();
++$this->callbackDepth;
try {
- $value = call_user_func_array( $callback, [ $curValue, &$ttl, &$setOpts, $asOf ] );
+ $value = $callback(
+ ( $curInfo['version'] === $version ) ? $curValue : false,
+ $ttl,
+ $setOpts,
+ ( $curInfo['version'] === $version ) ? $curInfo['asOf'] : null
+ );
} finally {
--$this->callbackDepth;
}
- $valueIsCacheable = ( $value !== false && $ttl >= 0 );
+ $postCallbackTime = $this->getCurrentTime();
- if ( $valueIsCacheable ) {
- $ago = max( $this->getCurrentTime() - $initialTime, 0.0 );
- $this->stats->timing( "wanobjectcache.$kClass.regen_set_delay", 1000 * $ago );
+ // How long it took to fetch, validate, and generate the value
+ $elapsed = max( $postCallbackTime - $initialTime, 0.0 );
+ // Attempt to save the newly generated value if applicable
+ if (
+ // Callback yielded a cacheable value
+ ( $value !== false && $ttl >= 0 ) &&
+ // Current thread was not raced out of a regeneration lock or key is tombstoned
+ ( !$useRegenerationLock || $hasLock || $isKeyTombstoned ) &&
+ // Key does not appear to be undergoing a set() stampede
+ $this->checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock )
+ ) {
+ // How long it took to generate the value
+ $walltime = max( $postCallbackTime - $preCallbackTime, 0.0 );
+ $this->stats->timing( "wanobjectcache.$kClass.regen_walltime", 1e3 * $walltime );
+ // If the key is write-holed then use the (volatile) interim key as an alternative
if ( $isKeyTombstoned ) {
- if ( $this->checkAndSetCooloff( $key, $kClass, $ago, $lockTSE, $hasLock ) ) {
- // Use the interim key value since the key is tombstoned (write-holed)
- $tempTTL = max( self::INTERIM_KEY_TTL, (int)$lockTSE );
- $this->setInterimValue( $key, $value, $tempTTL, $this->getCurrentTime() );
- }
- } elseif ( !$useMutex || $hasLock ) {
- if ( $this->checkAndSetCooloff( $key, $kClass, $ago, $lockTSE, $hasLock ) ) {
- $setOpts['creating'] = ( $curValue === false );
- // Save the value unless a lock-winning thread is already expected to do that
- $setOpts['lockTSE'] = $lockTSE;
- $setOpts['staleTTL'] = $staleTTL;
- // Use best known "since" timestamp if not provided
- $setOpts += [ 'since' => $preCallbackTime ];
- // Update the cache; this will fail if the key is tombstoned
- $this->set( $key, $value, $ttl, $setOpts );
- }
+ $this->setInterimValue( $key, $value, $lockTSE, $version, $walltime );
+ } else {
+ $finalSetOpts = [
+ 'since' => $setOpts['since'] ?? $preCallbackTime,
+ 'version' => $version,
+ 'staleTTL' => $staleTTL,
+ 'lockTSE' => $lockTSE, // informs lag vs performance trade-offs
+ 'creating' => ( $curValue === false ), // optimization
+ 'walltime' => $walltime
+ ] + $setOpts;
+ $this->set( $key, $value, $ttl, $finalSetOpts );
}
}
$this->cache->changeTTL( self::MUTEX_KEY_PREFIX . $key, (int)$initialTime - 60 );
}
- $miss = is_infinite( $minTime ) ? 'renew' : 'miss';
+ $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
$this->stats->increment( "wanobjectcache.$kClass.$miss.compute" );
- return $value;
+ return [ $value, $version, $curInfo['asOf'] ];
}
/**
* @return bool Whether it is OK to proceed with a key set operation
*/
private function checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock ) {
+ $this->stats->timing( "wanobjectcache.$kClass.regen_set_delay", 1e3 * $elapsed );
+
// If $lockTSE is set, the lock was bypassed because there was no stale/interim value,
// and $elapsed indicates that regeration is slow, then there is a risk of set()
// stampedes with large blobs. With a typical scale-out infrastructure, CPU and query
* @return array (current time left or null, UNIX timestamp of last purge or null)
* @note Callable type hints are not used to avoid class-autoloading
*/
- protected function resolveCTL( $value, $curTTL, $curInfo, $touchedCallback ) {
+ private function resolveCTL( $value, $curTTL, $curInfo, $touchedCallback ) {
if ( $touchedCallback === null || $value === false ) {
return [ $curTTL, max( $curInfo['tombAsOf'], $curInfo['lastCKPurge'] ) ];
}
- if ( !is_callable( $touchedCallback ) ) {
- throw new InvalidArgumentException( "Invalid expiration callback provided." );
- }
-
$touched = $touchedCallback( $value );
if ( $touched !== null && $touched >= $curInfo['asOf'] ) {
$curTTL = min( $curTTL, self::TINY_NEGATIVE, $curInfo['asOf'] - $touched );
* @return float|null UNIX timestamp of last purge or null
* @note Callable type hints are not used to avoid class-autoloading
*/
- protected function resolveTouched( $value, $lastPurge, $touchedCallback ) {
- if ( $touchedCallback === null || $value === false ) {
- return $lastPurge;
- }
-
- if ( !is_callable( $touchedCallback ) ) {
- throw new InvalidArgumentException( "Invalid expiration callback provided." );
- }
-
- return max( $touchedCallback( $value ), $lastPurge );
+ private function resolveTouched( $value, $lastPurge, $touchedCallback ) {
+ return ( $touchedCallback === null || $value === false )
+ ? $lastPurge // nothing to derive the "touched timestamp" from
+ : max( $touchedCallback( $value ), $lastPurge );
}
/**
* @param string $key
- * @param bool $versioned
- * @param float $minTime
- * @return array (cached value or false, cached value timestamp or null)
+ * @param float $minAsOf Minimum acceptable "as of" timestamp
+ * @return array (cached value or false, cache key metadata map)
*/
- protected function getInterimValue( $key, $versioned, $minTime ) {
- if ( !$this->useInterimHoldOffCaching ) {
- return [ false, null ]; // disabled
- }
+ private function getInterimValue( $key, $minAsOf ) {
+ $now = $this->getCurrentTime();
+
+ if ( $this->useInterimHoldOffCaching ) {
+ $wrapped = $this->cache->get( self::INTERIM_KEY_PREFIX . $key );
- $wrapped = $this->cache->get( self::INTERIM_KEY_PREFIX . $key );
- list( $value ) = $this->unwrap( $wrapped, $this->getCurrentTime() );
- $valueAsOf = $wrapped[self::FLD_TIME] ?? null;
- if ( $this->isValid( $value, $versioned, $valueAsOf, $minTime ) ) {
- return [ $value, $valueAsOf ];
+ list( $value, $keyInfo ) = $this->unwrap( $wrapped, $now );
+ if ( $this->isValid( $value, $keyInfo['asOf'], $minAsOf ) ) {
+ return [ $value, $keyInfo ];
+ }
}
- return [ false, null ];
+ return $this->unwrap( false, $now );
}
/**
* @param string $key
* @param mixed $value
- * @param int $tempTTL
- * @param float $newAsOf
+ * @param int $ttl
+ * @param int|null $version Value version number
+ * @param float $walltime How long it took to generate the value in seconds
*/
- protected function setInterimValue( $key, $value, $tempTTL, $newAsOf ) {
- $wrapped = $this->wrap( $value, $tempTTL, $newAsOf );
+ private function setInterimValue( $key, $value, $ttl, $version, $walltime ) {
+ $ttl = max( self::INTERIM_KEY_TTL, (int)$ttl );
+ $wrapped = $this->wrap( $value, $ttl, $version, $this->getCurrentTime(), $walltime );
$this->cache->merge(
self::INTERIM_KEY_PREFIX . $key,
function () use ( $wrapped ) {
return $wrapped;
},
- $tempTTL,
+ $ttl,
1
);
}
* // Map of cache keys to entity IDs
* $cache->makeMultiKeys(
* $this->fileVersionIds(),
- * function ( $id, WANObjectCache $cache ) {
+ * function ( $id ) use ( $cache ) {
* return $cache->makeKey( 'file-version', $id );
* }
* ),
* @param int $ttl Seconds to live for key updates
* @param callable $callback Callback the yields entity regeneration callbacks
* @param array $opts Options map
- * @return array Map of (cache key => value) in the same order as $keyedIds
+ * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
* @since 1.28
*/
final public function getMultiWithSetCallback(
ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
) {
- $valueKeys = array_keys( $keyedIds->getArrayCopy() );
- $checkKeys = $opts['checkKeys'] ?? [];
- $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
-
// Load required keys into process cache in one go
$this->warmupCache = $this->getRawKeysForWarmup(
- $this->getNonProcessCachedKeys( $valueKeys, $opts, $pcTTL ),
- $checkKeys
+ $this->getNonProcessCachedMultiKeys( $keyedIds, $opts ),
+ $opts['checkKeys'] ?? []
);
$this->warmupKeyMisses = 0;
* // Map of cache keys to entity IDs
* $cache->makeMultiKeys(
* $this->fileVersionIds(),
- * function ( $id, WANObjectCache $cache ) {
+ * function ( $id ) use ( $cache ) {
* return $cache->makeKey( 'file-version', $id );
* }
* ),
* @param int $ttl Seconds to live for key updates
* @param callable $callback Callback the yields entity regeneration callbacks
* @param array $opts Options map
- * @return array Map of (cache key => value) in the same order as $keyedIds
+ * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
* @since 1.30
*/
final public function getMultiWithUnionSetCallback(
ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
) {
- $idsByValueKey = $keyedIds->getArrayCopy();
- $valueKeys = array_keys( $idsByValueKey );
$checkKeys = $opts['checkKeys'] ?? [];
- $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
unset( $opts['lockTSE'] ); // incompatible
unset( $opts['busyValue'] ); // incompatible
// Load required keys into process cache in one go
- $keysGet = $this->getNonProcessCachedKeys( $valueKeys, $opts, $pcTTL );
- $this->warmupCache = $this->getRawKeysForWarmup( $keysGet, $checkKeys );
+ $keysByIdGet = $this->getNonProcessCachedMultiKeys( $keyedIds, $opts );
+ $this->warmupCache = $this->getRawKeysForWarmup( $keysByIdGet, $checkKeys );
$this->warmupKeyMisses = 0;
// IDs of entities known to be in need of regeneration
// Find out which keys are missing/deleted/stale
$curTTLs = [];
$asOfs = [];
- $curByKey = $this->getMulti( $keysGet, $curTTLs, $checkKeys, $asOfs );
- foreach ( $keysGet as $key ) {
+ $curByKey = $this->getMulti( $keysByIdGet, $curTTLs, $checkKeys, $asOfs );
+ foreach ( $keysByIdGet as $id => $key ) {
if ( !array_key_exists( $key, $curByKey ) || $curTTLs[$key] < 0 ) {
- $idsRegen[] = $idsByValueKey[$key];
+ $idsRegen[] = $id;
}
}
// Run the cache-aside logic using warmupCache instead of persistent cache queries
$values = [];
- foreach ( $idsByValueKey as $key => $id ) { // preserve order
+ foreach ( $keyedIds as $key => $id ) { // preserve order
$values[$key] = $this->getWithSetCallback( $key, $ttl, $func, $opts );
}
*/
final public function reapCheckKey( $key, $purgeTimestamp, &$isStale = false ) {
$purge = $this->parsePurgeValue( $this->cache->get( self::TIME_KEY_PREFIX . $key ) );
- if ( $purge && $purge[self::FLD_TIME] < $purgeTimestamp ) {
+ if ( $purge && $purge[self::PURGE_TIME] < $purgeTimestamp ) {
$isStale = true;
$this->logger->warning( "Reaping stale check key '$key'." );
$ok = $this->cache->changeTTL( self::TIME_KEY_PREFIX . $key, self::TTL_SECOND );
}
/**
- * @param array $entities List of entity IDs
- * @param callable $keyFunc Callback yielding a key from (entity ID, this WANObjectCache)
- * @return ArrayIterator Iterator yielding (cache key => entity ID) in $entities order
+ * Hash a possibly long string into a suitable component for makeKey()/makeGlobalKey()
+ *
+ * @param string $component A raw component used in building a cache key
+ * @return string 64 character HMAC using a stable secret for public collision resistance
+ * @since 1.34
+ */
+ public function hash256( $component ) {
+ return hash_hmac( 'sha256', $component, $this->secret );
+ }
+
+ /**
+ * Get an iterator of (cache key => entity ID) for a list of entity IDs
+ *
+ * The callback takes an ID string and returns a key via makeKey()/makeGlobalKey().
+ * There should be no network nor filesystem I/O used in the callback. The entity
+ * ID/key mapping must be 1:1 or an exception will be thrown. If hashing is needed,
+ * then use the hash256() method.
+ *
+ * Example usage for the default keyspace:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $modules,
+ * function ( $module ) use ( $cache ) {
+ * return $cache->makeKey( 'module-info', $module );
+ * }
+ * );
+ * @endcode
+ *
+ * Example usage for mixed default and global keyspace:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $filters,
+ * function ( $filter ) use ( $cache ) {
+ * return ( strpos( $filter, 'central:' ) === 0 )
+ * ? $cache->makeGlobalKey( 'regex-filter', $filter )
+ * : $cache->makeKey( 'regex-filter', $filter )
+ * }
+ * );
+ * @endcode
+ *
+ * Example usage with hashing:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $urls,
+ * function ( $url ) use ( $cache ) {
+ * return $cache->makeKey( 'url-info', $cache->hash256( $url ) );
+ * }
+ * );
+ * @endcode
+ *
+ * @see WANObjectCache::makeKey()
+ * @see WANObjectCache::makeGlobalKey()
+ * @see WANObjectCache::hash256()
+ *
+ * @param string[]|int[] $ids List of entity IDs
+ * @param callable $keyCallback Function returning makeKey()/makeGlobalKey() on the input ID
+ * @return ArrayIterator Iterator of (cache key => ID); order of $ids is preserved
+ * @throws UnexpectedValueException
* @since 1.28
*/
- final public function makeMultiKeys( array $entities, callable $keyFunc ) {
- $map = [];
- foreach ( $entities as $entity ) {
- $map[$keyFunc( $entity, $this )] = $entity;
+ final public function makeMultiKeys( array $ids, $keyCallback ) {
+ $idByKey = [];
+ foreach ( $ids as $id ) {
+ // Discourage triggering of automatic makeKey() hashing in some backends
+ if ( strlen( $id ) > 64 ) {
+ $this->logger->warning( __METHOD__ . ": long ID '$id'; use hash256()" );
+ }
+ $key = $keyCallback( $id, $this );
+ // Edge case: ignore key collisions due to duplicate $ids like "42" and 42
+ if ( !isset( $idByKey[$key] ) ) {
+ $idByKey[$key] = $id;
+ } elseif ( (string)$id !== (string)$idByKey[$key] ) {
+ throw new UnexpectedValueException(
+ "Cache key collision; IDs ('$id','{$idByKey[$key]}') map to '$key'"
+ );
+ }
+ }
+
+ return new ArrayIterator( $idByKey );
+ }
+
+ /**
+ * Get an (ID => value) map from (i) a non-unique list of entity IDs, and (ii) the list
+ * of corresponding entity values by first appearance of each ID in the entity ID list
+ *
+ * For use with getMultiWithSetCallback() and getMultiWithUnionSetCallback().
+ *
+ * *Only* use this method if the entity ID/key mapping is trivially 1:1 without exception.
+ * Key generation method must utitilize the *full* entity ID in the key (not a hash of it).
+ *
+ * Example usage:
+ * @code
+ * $poems = $cache->getMultiWithSetCallback(
+ * $cache->makeMultiKeys(
+ * $uuids,
+ * function ( $uuid ) use ( $cache ) {
+ * return $cache->makeKey( 'poem', $uuid );
+ * }
+ * ),
+ * $cache::TTL_DAY,
+ * function ( $uuid ) use ( $url ) {
+ * return $this->http->run( [ 'method' => 'GET', 'url' => "$url/$uuid" ] );
+ * }
+ * );
+ * $poemsByUUID = $cache->multiRemap( $uuids, $poems );
+ * @endcode
+ *
+ * @see WANObjectCache::makeMultiKeys()
+ * @see WANObjectCache::getMultiWithSetCallback()
+ * @see WANObjectCache::getMultiWithUnionSetCallback()
+ *
+ * @param string[]|int[] $ids Entity ID list makeMultiKeys()
+ * @param mixed[] $res Result of getMultiWithSetCallback()/getMultiWithUnionSetCallback()
+ * @return mixed[] Map of (ID => value); order of $ids is preserved
+ * @since 1.34
+ */
+ final public function multiRemap( array $ids, array $res ) {
+ if ( count( $ids ) !== count( $res ) ) {
+ // If makeMultiKeys() is called on a list of non-unique IDs, then the resulting
+ // ArrayIterator will have less entries due to "first appearance" de-duplication
+ $ids = array_keys( array_flip( $ids ) );
+ if ( count( $ids ) !== count( $res ) ) {
+ throw new UnexpectedValueException( "Multi-key result does not match ID list" );
+ }
}
- return new ArrayIterator( $map );
+ return array_combine( $ids, $res );
}
/**
* This must set the key to "PURGED:<UNIX timestamp>:<holdoff>"
*
* @param string $key Cache key
- * @param int $ttl How long to keep the tombstone [seconds]
+ * @param int $ttl Seconds to keep the tombstone around
* @param int $holdoff HOLDOFF_* constant controlling how long to ignore sets for this key
* @return bool Success
*/
/**
* @param string $key
- * @param int $ttl
+ * @param int $ttl Seconds to live
* @param callable $callback
* @param array $opts
* @return bool Success
+ * @note Callable type hints are not used to avoid class-autoloading
*/
private function scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) {
if ( !$this->asyncHandler ) {
// Update the cache value later, such during post-send of an HTTP request
$func = $this->asyncHandler;
$func( function () use ( $key, $ttl, $callback, $opts ) {
- $asOf = null; // unused
$opts['minAsOf'] = INF; // force a refresh
- $this->doGetWithSetCallback( $key, $ttl, $callback, $opts, $asOf );
+ $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
} );
return true;
* @param int $graceTTL Consider using stale values if $curTTL is greater than this
* @return bool
*/
- protected function isAliveOrInGracePeriod( $curTTL, $graceTTL ) {
+ private function isAliveOrInGracePeriod( $curTTL, $graceTTL ) {
if ( $curTTL > 0 ) {
return true;
} elseif ( $graceTTL <= 0 ) {
* Check if $value is not false, versioned (if needed), and not older than $minTime (if set)
*
* @param array|bool $value
- * @param bool $versioned
* @param float $asOf The time $value was generated
- * @param float $minTime The last time the main value was generated (0.0 if unknown)
+ * @param float $minAsOf Minimum acceptable "as of" timestamp
* @param float|null $purgeTime The last time the value was invalidated
* @return bool
*/
- protected function isValid( $value, $versioned, $asOf, $minTime, $purgeTime = null ) {
+ protected function isValid( $value, $asOf, $minAsOf, $purgeTime = null ) {
// Avoid reading any key not generated after the latest delete() or touch
- $safeMinTime = max( $minTime, $purgeTime + self::TINY_POSTIVE );
+ $safeMinAsOf = max( $minAsOf, $purgeTime + self::TINY_POSTIVE );
if ( $value === false ) {
return false;
- } elseif ( $versioned && !isset( $value[self::VFLD_VERSION] ) ) {
- return false;
- } elseif ( $safeMinTime > 0 && $asOf < $minTime ) {
+ } elseif ( $safeMinAsOf > 0 && $asOf < $minAsOf ) {
return false;
}
}
/**
- * Do not use this method outside WANObjectCache
- *
* @param mixed $value
- * @param int $ttl [0=forever]
+ * @param int $ttl Seconds to live or zero for "indefinite"
+ * @param int|null $version Value version number or null if not versioned
* @param float $now Unix Current timestamp just before calling set()
+ * @param float $walltime How long it took to generate the value in seconds
* @return array
*/
- protected function wrap( $value, $ttl, $now ) {
- return [
- self::FLD_VERSION => self::VERSION,
+ private function wrap( $value, $ttl, $version, $now, $walltime ) {
+ // Returns keys in ascending integer order for PHP7 array packing:
+ // https://nikic.github.io/2014/12/22/PHPs-new-hashtable-implementation.html
+ $wrapped = [
+ self::FLD_FORMAT_VERSION => self::VERSION,
self::FLD_VALUE => $value,
self::FLD_TTL => $ttl,
self::FLD_TIME => $now
];
+ if ( $version !== null ) {
+ $wrapped[self::FLD_VALUE_VERSION] = $version;
+ }
+ if ( $walltime >= self::GENERATION_SLOW_SEC ) {
+ $wrapped[self::FLD_GENERATION_TIME] = $walltime;
+ }
+
+ return $wrapped;
}
/**
- * Do not use this method outside WANObjectCache
- *
- * The cached value will be false if absent/tombstoned/malformed
- *
- * @param array|string|bool $wrapped
+ * @param array|string|bool $wrapped The entry at a cache key
* @param float $now Unix Current timestamp (preferrably pre-query)
- * @return array (cached value or false, current TTL, value timestamp, tombstone timestamp)
+ * @return array (value or false if absent/tombstoned/malformed, value metadata map).
+ * The cache key metadata includes the following metadata:
+ * - asOf: UNIX timestamp of the value or null if there is no value
+ * - curTTL: remaining time-to-live (negative if tombstoned) or null if there is no value
+ * - version: value version number or null if the if there is no value
+ * - tombAsOf: UNIX timestamp of the tombstone or null if there is no tombstone
*/
- protected function unwrap( $wrapped, $now ) {
- // Check if the value is a tombstone
- $purge = $this->parsePurgeValue( $wrapped );
- if ( $purge !== false ) {
- // Purged values should always have a negative current $ttl
- $curTTL = min( $purge[self::FLD_TIME] - $now, self::TINY_NEGATIVE );
- return [ false, $curTTL, null, $purge[self::FLD_TIME] ];
- }
-
- if ( !is_array( $wrapped ) // not found
- || !isset( $wrapped[self::FLD_VERSION] ) // wrong format
- || $wrapped[self::FLD_VERSION] !== self::VERSION // wrong version
- ) {
- return [ false, null, null, null ];
- }
-
- if ( $wrapped[self::FLD_TTL] > 0 ) {
- // Get the approximate time left on the key
- $age = $now - $wrapped[self::FLD_TIME];
- $curTTL = max( $wrapped[self::FLD_TTL] - $age, 0.0 );
+ private function unwrap( $wrapped, $now ) {
+ $value = false;
+ $info = [ 'asOf' => null, 'curTTL' => null, 'version' => null, 'tombAsOf' => null ];
+
+ if ( is_array( $wrapped ) ) {
+ // Entry expected to be a cached value; validate it
+ if (
+ ( $wrapped[self::FLD_FORMAT_VERSION] ?? null ) === self::VERSION &&
+ $wrapped[self::FLD_TIME] >= $this->epoch
+ ) {
+ if ( $wrapped[self::FLD_TTL] > 0 ) {
+ // Get the approximate time left on the key
+ $age = $now - $wrapped[self::FLD_TIME];
+ $curTTL = max( $wrapped[self::FLD_TTL] - $age, 0.0 );
+ } else {
+ // Key had no TTL, so the time left is unbounded
+ $curTTL = INF;
+ }
+ $value = $wrapped[self::FLD_VALUE];
+ $info['version'] = $wrapped[self::FLD_VALUE_VERSION] ?? null;
+ $info['asOf'] = $wrapped[self::FLD_TIME];
+ $info['curTTL'] = $curTTL;
+ }
} else {
- // Key had no TTL, so the time left is unbounded
- $curTTL = INF;
- }
-
- if ( $wrapped[self::FLD_TIME] < $this->epoch ) {
- // Values this old are ignored
- return [ false, null, null, null ];
+ // Entry expected to be a tombstone; parse it
+ $purge = $this->parsePurgeValue( $wrapped );
+ if ( $purge !== false ) {
+ // Tombstoned keys should always have a negative current $ttl
+ $info['curTTL'] = min( $purge[self::PURGE_TIME] - $now, self::TINY_NEGATIVE );
+ $info['tombAsOf'] = $purge[self::PURGE_TIME];
+ }
}
- return [ $wrapped[self::FLD_VALUE], $curTTL, $wrapped[self::FLD_TIME], null ];
+ return [ $value, $info ];
}
/**
- * @param array $keys
+ * @param string[] $keys
* @param string $prefix
- * @return string[]
+ * @return string[] Prefix keys; the order of $keys is preserved
*/
protected static function prefixCacheKeys( array $keys, $prefix ) {
$res = [];
* @param string $key String of the format <scope>:<class>[:<class or variable>]...
* @return string A collection name to describe this class of key
*/
- protected function determineKeyClassForStats( $key ) {
+ private function determineKeyClassForStats( $key ) {
$parts = explode( ':', $key, 3 );
return $parts[1] ?? $parts[0]; // sanity
* @return array|bool Array containing a UNIX timestamp (float) and holdoff period (integer),
* or false if value isn't a valid purge value
*/
- protected function parsePurgeValue( $value ) {
+ private function parsePurgeValue( $value ) {
if ( !is_string( $value ) ) {
return false;
}
}
return [
- self::FLD_TIME => (float)$segments[1],
- self::FLD_HOLDOFF => (int)$segments[2],
+ self::PURGE_TIME => (float)$segments[1],
+ self::PURGE_HOLDOFF => (int)$segments[2],
];
}
* @param int $holdoff In seconds
* @return string Wrapped purge value
*/
- protected function makePurgeValue( $timestamp, $holdoff ) {
+ private function makePurgeValue( $timestamp, $holdoff ) {
return self::PURGE_VAL_PREFIX . (float)$timestamp . ':' . (int)$holdoff;
}
* @param string $group
* @return MapCacheLRU
*/
- protected function getProcessCache( $group ) {
+ private function getProcessCache( $group ) {
if ( !isset( $this->processCaches[$group] ) ) {
- list( , $n ) = explode( ':', $group );
- $this->processCaches[$group] = new MapCacheLRU( (int)$n );
+ list( , $size ) = explode( ':', $group );
+ $this->processCaches[$group] = new MapCacheLRU( (int)$size );
}
return $this->processCaches[$group];
}
/**
- * @param array $keys
+ * @param string $key
+ * @param int $version
+ * @return string
+ */
+ private function getProcessCacheKey( $key, $version ) {
+ return $key . ' ' . (int)$version;
+ }
+
+ /**
+ * @param ArrayIterator $keys
* @param array $opts
- * @param int $pcTTL
- * @return array List of keys
+ * @return string[] Map of (ID => cache key)
*/
- private function getNonProcessCachedKeys( array $keys, array $opts, $pcTTL ) {
- $keysFound = [];
- if ( isset( $opts['pcTTL'] ) && $opts['pcTTL'] > 0 && $this->callbackDepth == 0 ) {
- $pcGroup = $opts['pcGroup'] ?? self::PC_PRIMARY;
- $procCache = $this->getProcessCache( $pcGroup );
- foreach ( $keys as $key ) {
- if ( $procCache->has( $key, $pcTTL ) ) {
- $keysFound[] = $key;
+ private function getNonProcessCachedMultiKeys( ArrayIterator $keys, array $opts ) {
+ $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
+
+ $keysMissing = [];
+ if ( $pcTTL > 0 && $this->callbackDepth == 0 ) {
+ $version = $opts['version'] ?? null;
+ $pCache = $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY );
+ foreach ( $keys as $key => $id ) {
+ if ( !$pCache->has( $this->getProcessCacheKey( $key, $version ), $pcTTL ) ) {
+ $keysMissing[$id] = $key;
}
}
}
- return array_diff( $keys, $keysFound );
+ return $keysMissing;
}
/**
- * @param array $keys
- * @param array $checkKeys
- * @return array Map of (cache key => mixed)
+ * @param string[] $keys
+ * @param string[]|string[][] $checkKeys
+ * @return string[] List of cache keys
*/
private function getRawKeysForWarmup( array $keys, array $checkKeys ) {
if ( !$keys ) {
dépôts / lhc / web / wiklou.git / blobdiff